1. Field of the Invention
The present invention relates to a golf club head structured by using a metal material and a fiber reinforced resin, and a manufacturing method of the same.
2. Prior Art
There have been proposed various golf club heads in which a fiber reinforced resin member is combined in a part of a metal material member which is main part of the golf club head (hereinafter, this may be sometimes called simply as “combined head”). A weight of the combined head can be reduced by using the parts made of a fiber reinforced resin having a small specific gravity, and there is an advantage that a freedom of designing a weight distribution of the head can be improved by allocating the reduced weight to a side portion of the head, for example, a toe or a heel, or allocating to a back face.
Further, the combined head can be manufactured by adhering a resin member made of a fiber reinforced resin and previously molded in a predetermined shape, for example, to an opening portion of a head shell portion made of a metal material, (hereinafter, this manufacturing method may be sometimes called simply as “adhesive bonding method”). However, in accordance with the adhesive bonding method, a gap or a step tends to be formed on the boundary of a junction between the head shell portion and the resin member, and an outer appearance and a showing of the head tend to be deteriorated. Further, there is a risk that a fitting of both the members does not stabilize due to a dispersion in manufacturing the head shell portion and/or the resin member, and there is a risk that an adhesive strength is lowered, by extension. If the adhesive strength is lowered, the resin member tends to come off from the head shell portion due to an impact force at a time of hitting a ball.
As the other method of manufacturing the combined head, there has been known a so-called internal pressure molding method (refer, for example, to Japanese Unexamined Patent Publication No. 2001-190716 and Japanese Unexamined Patent Publication No. 2001-190718). The internal pressure molding method heats a head base body formed by arranging a laminated body P comprising a plurality of prepregs under a partially cured state in an opening portion O1 of a head shell portion M made of a metal material, as shown in FIG. 7A, in a metal mold 20 as shown in FIG. 7B, and inflates a bladder B in a hollow portion i. Accordingly, the laminated body P is exposed to a heat energy and a pressure, is strongly pressed against a cavity side of the metal mold 20 so as to be formed in a predetermined shape, and is firmly fixed to a periphery of the opening portion O1 of the head shell portion M. In accordance with the internal pressure molding method mentioned above, it is possible to reduce the gap or the step on the boundary between the head shell portion M and the resin member FR as much as possible as is different from the adhesive bonding method, and it is possible to provide a head having an improved appearance.
However, the internal pressure molding method has the following disadvantage. In other words, in accordance with the internal pressure molding method, in order to make the laminated body P of the prepreg closely contact with the surfaci of the cavity C of the metal mold 20, it is necessary to expand to an outer side comparatively largely. For this purpose, it is necessary to uniformly apply a pressure to the laminated body P of the prepreg from an inner side. However, there is a case that a temporal shift is generated in each of portions in the contact between the bladder B and the laminated body P at a time of inflating the bladder B, whereby an uneven internal pressure is applied to the laminated body P. As a result, the laminated body P can not uniformly inflate to the outer side, and a defect in molding such as a crimple and a concavity and convexity is generated on a surface of the molded resin member. Further, since not only the crimple and the concavity and convexity generate a problem in the outer appearance, but also the reinforced fiber in this part is folded, it is impossible to obtain a sufficient strength and the crimple and the concavity and convexity tend to generate a starting point of a damage.